Designs by George Miles

During World War II the British Fleet Air Arm had problems with
its deck landings. The accident rate was high. George Miles thought
that there were 3 essentials about carrier airplanes.

a good view

a strong landing gear

overall small size for better storage and access to the deck
elevators.

He got his inspiration after seeing the Westland Lysander P12
"Duo-Mono". This plane (concept by Maurice H. Delanne), which was a
conventional airplane with a large tail, have the possibility to
place the center of gravity (CG) more backwards. It wasn't a
tandem, but that idea began to get shaped in Miles'
brain.

I found in Air Enthusiast / number five (a magazine) the
following list of advantages Miles thought to create with his
tandem.

By locating the engine amidships to drive a pusher propeller,
the pilot could be positioned in the nose and thus provided with
the perfect, unobstructed view for deck
operations.

The division of lift between two wings and the prospect of
achieving an increased overall Cl (lift
coefficient) made it possible to restrict the wing span to
the size of the carrier lift and thus elimination the
weight and complexity of wing folding.

The elimination of the conventional tail and the concentration
of power plant weight near the CG would result in
considerable reductions in both length and structural
weight, which, in combination with (B), should also result
in increased maneuverability.

Both foreplane and aftplane would contribute to total lift and
consequently the parasite drag associated with a
conventional tailplane would be eliminated - this often
amounting to as much as 10 per cent of the total drag of a clean
aircraft.

With the conventional wing-tailplane arrangement, the nosedown
pitching moment associated with the center of pressure movement due
to increased incidence calls for maximum negative lift from the
tailplane at the very moment when the greatest overall lift is
desired, but with the true tandem-wing arrangement the lift of the
two planes would be additive and backward movement of the CP would
call for increased lift from the leading plane to maintain
trim.

This may sound like Chinese to some. So, let us review the
lines.

Placing the engine behind the pilot would really improve the
view of a pilot during landings. So see the W.W.II Corsair. If that
engine didn't block the pilots view...

Hmm. Increase of total lift coefficient (Cl). I thought it
would increase as well, because there no longer is a downwards
lifting tail. But I don't have the numbers to justify or kill this
thought.

This one puzzles me. I can understand that less weight leads to
better maneuverability. Just imagine two bikes. One is a ordinary
bike, the other is a bike with your sister on the back and your
brother on the front. Which bike would perform best when riding a
path in the form of a 8. The first of course! But I can not
understand how a better total Cl can improve maneuverability.

Question: Can anyone clear this one out for me?
Answer: (from J.T. Wenting / jwenting@hornet.demon.nl /
www.hornet.demon.nl) "As I see it, increased lift (Ci) will mean
not so much increased agility, but the ability to maneuver at lower
speeds, thus reducing landing speed, which is vitally important
aboard carriers. In WWII aircraft, the high landing speeds were
being seen as a problem, especially for carrier operations.
Reducing landing speed would make the aircraft easier to handle
during approach to a carrier landing. At the same time, the
aircraft would become more agile during a dogfight, as those
normally take place at relatively low speed (or if they start at
high speed, that speed bleeds of as energy is consumed in
turning. An aircraft that can still maneuver at low
speeds while it's opponent cannot, may well win out in a turning
fight). As to landings, increased Ci can also decrease the nose-up
attitude during landings, making the runway/carrier deck more
easily visible to the pilot. The US Navy made a hybrid
out of this concept in the F-8 Crusader, by tilting the wing
several degrees during landing to allow the pilot to remain almost
level during the approach, thus allowing him a better view of the
carrier deck then would have been possible otherwise given the high
stalling speed of the aircraft."

I got another remark about maneuverability by Evan L. Mayerle.
It is not Cl related, but interesting to know anyhow. A: "Well,
first of all, concentrating all your heavy items, like the engine,
near the cg is going to reduce your moments of inertia so that a
given input will get more output. By the same token, splitting the
lift between two wings, especially if the split can be controlled
or varied, can also enhance maneuverability. I don't think that an
increased Cl can, of itself, increase maneuverability; however,
it's been decades since I took any Aero. classes and my work has
been mostly detail design, not overall configuration." The time
when I did receive this mail the text above was not yet placed. So
he could not have known about the relation J.T. Wenting
mentioned.

I can understand that many would react "But the plane still has
two surfaces?! ". OK, lets make a little experiment. Imagine that
we choose a airfoil with a 10 % height / length ratio. Now, choose
a certain wing area (make it a round number to keep the
calculations simple). Start drawing this wing in several shapes and
calculate the frontal area. After a few drawings you will see that
there is no change in frontal area. Even dividing the wing in 2 of
more wings does not change the frontal area. Miles did divide the
wing into 2. These two wings have their own compensation of the
natural pitching moment of a wing. So they don't need to have a
downwards pushing tail. No tail means less frontal area and that
means less drag. But watch out with the experiment. There is a
catch. If you change the chord length, you also change the lift a
wing can generate. Shorter airfoils have lower lift/drag ratio. The
maximum Cl becomes less. So drawing a wing the same wing area but
using a shorter chord will give less lift. To get the same lift as
before you need to have more wing area. More wing area means more
frontal area, more frontal area means more drag. Still Chinese?
Give me a sign. I will insert more info on this item.

Translated to human language this means that if the angle of
attack (AoA)( = the angle between the roll axis of the plane and a
horizontal) increases the place of the lift force shifts more
backwards. Really... it does! Conventional airplanes need to
compensate this moment (generated by the lift force being more
backward from the CG) with a increasing downward force at the tail.
Because higher AoA are being used at landings, this is not ideal.
At landings you need to get as much lift out of your airplane as it
can get at those lower speeds. Tandems also get this extra moment,
but they can compensate it by creating more LIFT on the front wing.
Just as I like it

George Miles was very, very enthusiast about this tandem idea.
Seeing his advantages, who wouldn't be? But would the plane be
stable? He still had to prove. Miles knew this and made a
proof-of-concept airplane to get support for his Fleet fighter
proposal. He made the M 35 in 1942 as a private venture without the
knowledge of the Ministry of Aircraft Production. Roll-out was at
the end of April 1942 after only 6 weeks from the start of the
build up. This was possible due to the extensive use of existing
parts (NASA today uses this strategy as much as possible when
making their X-planes).

Miles flew the plane himself on its flight flight. It nearly
ended in disaster. It was very unstable around its pitch axis. Even
after ballasting, which improved stability, the overall result was
still not so good. But Miles thought it had proven his idea.
Windtunnel tests would have showed this instability, but I guess
Miles was in a hurry.He didn't get official support for his Fleet
fighter. But that didn't stop Miles. He proposed a tandem design, M
39, for the specification B.11/41. This was suggested by the
Ministry who wanted a high speed, high altitude bomber possessing a
range of 2414 km (1500 miles) at an altitude of 9145 m (30 000 ft)
and a bomb load of 1814 kg (4000 lb.). Miles didn't get official
support again. But Miles wouldn't be Miles if he didn't make a
scale model as a private venture. This scaled-down (5/8) airplane,
the M39B, was a twin-engine airplane with its engines mounted on
the rear wing. A unusual thing to do at those days.The wings were
changed from position when related to the M35. The front wing was
now placed lower and the rear wing was placed higher. This was
simply because the prop needed ground clearance.The ratio between
the wing areas changed also. The M35 had a ratio of 1:2, the M39B
had a ratio of 1:3. This change was done after the first
evaluations of the M35.

After viewing the M39B the Ministry got interested in the tandem
design and bought the plane to test it.

Now let us see the situation. We have two wings. How would you
position the control surfaces? ... Miles did it as following: flaps
on both wings, elevators on the front wing, ailerons on the rear
wing and rudders at the wingtips and there also was a non-moving
tail at the end of the fuselage. Elevators and ailerons were
positioned next to the flaps, which were placed next to the
fuselage.How did this influence the flight characteristics? Well,
on the ground all was well, thanks to the three cycle landing gear
with steerable nose wheel and rudders, which were placed not in the
prop wash. Conventional airplanes have a tendency to swing because
their tail is placed in the prop wash (see drawing in the
asymmetric section). The M39B did not swing.The double flaps were
something complex. The front flap made nose-ups, the rear flap made
nose-downs. They had to be used together. Positive news was that if
they were positioned correctly take-off occurred without moving the
stick at 109 km/h (68 mph) and this flap setting could be used
during the climb. Sounds rather easy to me.

But the thing that interested the Ministry was its stall
behavior. You couldn't stall the M39B if the flaps were placed in
its neutral position. The Ministry asked more tests to explore this
non-stall behavior. Pilots founds out that it got lost when flaps
were being used. It was even so that if the M39B stalled, it
happened without warning! So it was good news and bad news. Later
more about the good news (when talking about the designs of Henri
Mignet).Tests were also done with one engine stopped. The loss of
the port (left) engine could just be controlled, but the loss of
the starboard (right) engine caused problems. Loss of a engine
could lead to a very steep "graveyard" spiral, especially with the
loss of the right engine.Flying the M39B in turbulence was not a
pleasure. But a landing approach was a delight due to the good view
(just as Miles waned). But the not so good rudder response made it
hard to keep the plane in line with the airstrip during crosswinds.
You had to use much rudder. Knowing that the steerable nose wheel
was linked with the rudder control, you can imagine the smack the
pilot got in his leg when that (not in center) wheel hit the
ground.

The M39B was a scaled down version of the bomber proposal of
Miles. So it wasn't stressed for acrobatics. On one of the flight a
pilot encountered some turbulence. He later said it felt like the
cockpit wanted to break off.

It will not be a surprise if I tell you that there were no
orders for the M39. In fact, the whole specification B.11/41
lapsed.

This story of a "new" (see later) concept, which didn't get
orders but was build twice without official support, shows that a
designer can sometimes be so enthusiast about his proposal, that he
is blinded from the fact that there is still a lot of work on the
design. Just to mention: Miles' firm went into liquidation in
1948.

Was it his stubborn behavior or the fact that after the war
there were no more demands for airplanes? I don't know. All info on
that item is welcome.